Ultrasonic Flow Measurement – Flow Details Tab on the Atrato Ultrasonic Meter
The large display reflects the meter readings showing on the Atrato LCD Display, if fitted and will mimic that display. The buttons either side have the functions selected on the ‘Configuration’ screen and also work in parallel with the buttons on the Atrato flowmeter unit itself. The small window below the rate and total display shows various relevant operational parameters whilst the unit is operating e.g. relay status and frequency output if these options are selected.
This is the instantaneous flow rate and is updated approximately every 100 milliseconds.
FILTERED FLOW RATE
This is the filtered flow rate and is identical to the LCD display on the flowmeter (if fitted) and the speed of change will depend on the filter setting. The filter will also affect the response time for the analogue outputs and the flow switches.
The total liquid passed since the last reset.
PIN 6 & 7:
If no selection is made “Not used” will be in the Notes column. See following text and chart for the display legends.
When Pin 6 or 7 is set to “Output” and set to “Pulse” this will display the frequency of the running output and the number of pulses per litre selected.
If it is selected to “Output” and set to “Flow switch” the Value column will show the transistor status either “low” or “high” and the notes will show the selected switch points.
If “Output” and “Reverse Flow” are selected the Value column will show either “low” or “high” depending on forward or reverse flow.
If “Input” is selected the Value column will show “high” or “low” depending on the switch condition and “Input Logic level” in the Notes column.
The chart below shows the various display messages for various operating functions. During operation only one message will be shown for each parameter.
PIN 7: The display for “Pin 7” will function the same as “Pin 6”.
RELAY: If no function is set for the relay the Value column will show “Off” otherwise it will display the function and its operating parameters.
There are 2 possibilities for the PIN protection:
To use these features it is first necessary to create a PIN. This is a four digit number in the range 0001 to 9999. Setting a value of 0000 tells the software there is no PIN and this is how to remove the PIN. After allocating a PIN these check boxes can lock all of the settings or just the advanced user, including the accumulated total reset. If you forget your PIN please contact you supplier for the default value. Once entered, all the setting parameters remain visible. In the ‘Help’ menu, the user can ‘Log On using PIN…’ but the user will be prompted for the PIN prior to making any changes. If the display version of the meter is being used and the display is set to view totals or rate and total the left hand button will cycle through the various options.
Rate The display shows units and time base e.g. 1.0 Ltr/min.
Total The display is static with just the volume e.g. 10.3Ltr.
This filter removes short term anomalies in the recorded e.g. an air bubble passing through. It should be used with caution as it is theoretically possible that over use of this feature could lead to incorrect results in certain circumstances. Under normal operating conditions the meter returns around 25 results per second and a regular occurrence at this frequency could be completely ignored thus causing problematic readings.
The filter is a moving window taking the middle number from an odd number of results selectable between 1 and 21. It is not an average or mean and it is designed to totally ignore one or more results.
The seventh flow in the table above is zero. This could have been a small bubble passing through the 710 meter which has a 1mm bore which could completely absorb the ultrasound. The median filter completely ignores this reading and for the zero reading returns the value of 3 from the results either side. This filter is particularly useful at low flows where a small dip in value could drop a result below the internal cut off levels.
SPEED OF SOUND COMPENSATION
The Atrato ultrasonic flowmeter is factory calibrated on clean water and therefore the window of calibration is based around the measured time of flight of the ultrasonic signal based on the speed of sound of water. When a fluid is used in the meter that has a significantly different speed of sound to that of water, the stable signal may move outside of the window causing the meter to read incorrect and unstable time of flight signals. In this scenario you can compensate by manually adjusting the measurement window of the meter in the advanced tab feature for Fluid Speed of Sound Adjustment. A bar is seen in the graph indicating whether a strong signal is being measured. If a fluid has a faster speed of sound the user can click the FASTER button to adjust the measurement window a stronger signal point. A RED graphic is a very poor signal, ORANGE indicates a weak signal and GREEN is a good strong signal.
The user then enters a simple scaling factor on the User Settings tab, to accurately adjust the water calibration to that of the fluid being measured.
Flow Meter Data Logging (not available on all meters)
For general diagnostic purposes it is possible to log the meter performance using the Data logging Tab function. The logging is not internal to the flowmeter, but stored to the connected PC and therefore only occurs whilst the PC is connected to the meter.
Simply tick the relevant parameter you wish to log, choose a sensible sampling period (i.e. for longer data-logging periods choose 10+ second intervals to limit the size of the file created), and then click the Icon under Storage File and enter a simple filename (no spaces) at a location you desire.
Once all is selected correctly the START LOGGING button will become enabled. Click it to start the datalogging file creation. In the bottom left corner the samples collected will be listed as the log file builds.
To finish the log file, simply Click STOP LOGGING.